The present invention relates to padlocks of the type comprising a padlock body or casing of elongated shape, and a detachable, U-shaped shackle with two arms adapted to become locked within the casing, using a cylinder-type locking device.
These padlocks are widely used, e.g. for locking shops, show-window protective grills, outdoor gates and the like.
The padlocks of the kind referred to are almost exclusively made of a hexagonal profiled bar usually cut from standard iron rods. The cut pieces are then machined in order to provide same with side openings for the shackle arms; with a cavity for accomodating the key-operated, cylinder-type locking device of any standard type, commercially available; with a blind bore for housing and rotatably supporting a lock rod which becomes engaged with suitable recesses formed in the shackle arms; and with an additional bore through which a screw-threaded bolt is adapted to be inserted for fastening the cylinder lock device within the lock casing.
In addition, after the various machining operations are completed, the lock body must undergo a heat treatment process to protect it against drilling, sawing and other such burglary attempts to which it might be exposed.
Finally the completed body must be polished in order to receive a metallic coating or electro-plating.
This processing of the lock body makes the product quite expensive on the one hand, and affects its suitability for mass production, on the other hand. Another deficiency of the conventional locks resides in that the various commercially available cylinder-locks are made so that the inner cylinder is free to rotate any number of turns. For adapting such locks to serve as padlock operating devices, special measures have to be taken to delimit the rotation of the key to a quarter of a revolution only. Usually this is attained by inserting an extra pin into the device casing.
Still in this context, in order to comply with security standards, the cylinder locking device must be provided with at least one--but usually more--anti-drill pins, to prevent tampering with the cylinder mechanism of the lock.
It is thus the general object of the invention to provide a method of manufacturing padlocks of the type referred to, consisting of fewer production stages--and therefore being less costly--without, however, affecting their security level relative to the conventional padlocks.
It is a further object of the invention to provide padlocks composed essentially of an inner member made of relatively soft and easy-to-process material, such as cast iron or nonferrous metals, on the one hand, and a sheath or cover of burglary-protected material such as hardened steel.
It is a still further object of the invention to provide such sheath being made of standard steel pipe length that need no processing other than hardening heat treatment.
It is a still further object of the invention to save the extra manufacturing costs of the rotation limiting means, on the one hand, and the safety pins, on the other hand, with which the cylinder lock device must be equipped before it can be used for the purpose in question.
In addition, it has been found that other advantages are attained regarding simplicity of manufacture and assembly as will be explained in detail below.